Intensifier for the application of power



Allg' 14, 1951 E. A. RocKwELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF POWER INVENTOR Edward A. Roc/nwe# YAMM 'ZK ATTORNE Allg' 14, 1951 E. A. RocKwELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF' POWER Filed OCT.. 20, 1943 16 Sheets-Sheet 2 ATTORNEY Filed Oct. 20, 1943 Aug 14, 1951 E. A. RocKWl-:LL 2,564,582

INTENSIFIER FOR THE APPLICATION OF' POWER 16 Sheets'-Sheet 5 INVENTOR Ecgward A. lockwel Allg 14, 1951 E. A. RocKwELL O 2,564,582

INTENSIF IER FOR THE APPLICATION OF' POWER Filed oct. 2o, 1943 16 sheetsheet 4 INVENTOR ATTORNEY Aug. 14, 1951 E. A. RocKwELL INTENSIFIER FOR THE APPLICATION OF' POWER 16 Sheets-Sheet 5 Filed Oct. 20, 1943 INVENTOR Edward 41. Rock welt ATTORNEY Aug. 14, 1951 E. A. RocKwELl.

INTENSIFIER FOR THE APPLICATION OF POWER 16 Sheets-Sheet 6 Filed OCC.- 20, 1943 n l L. Imm., Q. wwm m Nm Il p ?\\\ILQ v Allg 14, 1951 E. A. RocKwELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF POWER Filed Oct. 20, 1945 16 Sheets-Sheet 7 v INVENTOR /54 Edward A. Rockwe E. A. RocKwELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF POWER l 16 Sheets-Sheet 8 Aug. 14, 1951 Filed Oct. 20, 1945 222 22] f L. "Y l] l NVENTOR ATTORNEY Aug. 14, 1951 E. A. RocKwELl.

INTENSIFIER FOR THE APPLICATION OF POWER 16 Sheets-Sheet 9 Filed 0013. 20, 1943 mm SN w EN @MMM RN. www@ ATTORNEY INVENTOR Edward UQ. lockwe Allg 14, 1951 E. A. RocKwELL INTENSIFIER FOR THE APPLICATION oF PowER Filed oct. 2o, 194s 16 Sheets-Sheet 10 INVENTOR Edward .Roc/'wel E E -`Z t A ORNEY Aug. 14, 1951 E, A ROCKWELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF' POWER Filed 0G11. 20, 1945 16 Sheets-Sheet 11 Tr. an.

l .20/l 324 34 3303/7\`\ 3f@ 3V Q 348 346 3:9 323 l' I," 324, 3g 6 357 34 339 33;() bi 5 359 358 328 34] l l 29/ 3 /f 3336 37a 326 z 366 327 INVENTOR Edward Qjocwel ATTORNEY Aug- 14, 1951 E. A. RocKwELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF POWER Filed Oct. 20, 1943 16 Sheets-Sheet l2 'all' j-T. e5.

Line Pressure Muster Cylinder Pressure INVENTOR Edward .LROCu/e ATTORNEY Aug. 14, 1951 E. A. RocKwELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF POWER Filed Oct. 20, 1943 16 Sheets-Sheet 15 334 "Nm- $4/ 333 I INVENTOR Aug. 14, 1951 E. A. RocKwELL 2,564,582

INTENSIFIER FOR THE APPLICATION 0F POWER .t Filed oop. 2o, 194s 1mas.

16. Sheets-Sheet 14 INVENTOR M (AS/'mi- ATTORNEY ug- 14, 1951 E. A. ROCKWELL INTENSIFIER FOR THE APPLICATION OF POWER 16 SheetS-Sheet 15 Filed 0G11. 20, 1943 III.

QN m SN mmx W FII Walal mh mew a y IIIII IIIIIIIIII l.-- lill." Il nl 0 -lNvENToR Edward vlacwel( Aug. 14, 1951 E A ROCKWELL 2,564,582

INTENSIFIER FOR THE APPLICATION OF POWER Filed Oct. 20, 1945 16 Sheets-Sheet 16 ATTORNEY Patented A ug. 14, 1951 INTENSIFIER FOB THE APPLICATION F POW Edward A. Rockwell, Cleveland, Ohio Application October 20, 1943, Serial No. 507,227 v claims. (c1. so-54.5)

My invention relates to apparatus intended for the application of power for any desired purpose, so as to apply an intensiiled power thereto, but which is particularly advantageous in connection with the application of power to one or more parts, for example brakes, clutches, transmissions, etc., of automotive vehicles. airplanes, etc.

It is an object of my invention to provide an apparatus for intensifying power, capable of general application, although it is especially applicable, for example. in the operation of automotive vehicles, such as automobiles, airplanes, etc. A further object is to provide an improved form of apparatus oi.' this character over my previous application upon Intensifler Valve. Ser. No. 388,003, filed April 11, 1941, Patent No. 2,398,252, granted April 9, 1946. A further object of my invention is to provide an apparatus of this character so arranged as to enable a greater volume lo1 the hydraulic liquid to be delivered therefrom and with a more compact and short apparatus. Another object is to obtain these results with a larger stroke of the power applying element in the apparatus. Still another object is to operate the said apparatus with a vacuum or other pressure differing from the atmospheric pressure in cooperation with the atmospheric air pressure while llessening the effective volume required, of these pressure media. In other words, in my apparatus the movable wall or diaphragm which is used for applying power is operated in a chamber in which the clearance volume with regard to the diaphragm is reduced. Again, a further object is to provide an effective air bleeding of the seals in the apparatus so as to remove oil vapors. all of the air bleeding passages being connected together. Still another object is to provide an apparatus of this character capable of heavy duty. by utilizing a plurality of power units which are constructed, respectively, so as to obtain a higher degree of efficiency, for example in the operation of the brakes on heavy trucks. By using the two stages a much smaller amount of the vacuum is needed and, comparatively, the volume of the power applying units can be much smaller than in the case of using a single power unit to obtain the desired brake pressures with the needed volume of liquid for operating the brakes. This results in a saving of the accumulated vacuum. When using the two stages, furthermore, the second stage operates, when it cuts in, at the same time or con- Jointly with the first stage so that power is applied to the brakes simulaneously -from both of them.

- brakes.

Another improvement in my present invention over the subject matter of my previous application upon Intensiiier Valve, above referred to, is the arrangement of the movable wall or diaphragm in the power units in such a way that the said wall is in eilect floated in its retracted position, without resting initially against a positive stop. in order to avoid producing a sudden transition from the setting of the brakes by the manual hydraulic power applied thereto, to the application of the liquid under power to said This avoids a sudden transition from the movement of the brake shoes by merely the manual means to the power means, which would be perceptible evidencing itself in the form of a bump and being detrimental to the nicety of control in the absence of the gradual transition obtained in accordance with my present invention. This is accomplished by producing, as soon as the manual pressure is applied, a small retraction of the power plunger which is immediately taken up thereafter by the ilrst applicaton of the manual pressure. At the same time that the power plunger is retracted in this way. there is also a slight opening of the air valve to admit air in a relatively small amount to one side of the movable wall, which takes place before the liquidcompensating inlet valve in the power unit is closed by the increase of manual hydraulic pressure. A further improvement in my present apparatus is that I obtain a greater sensitiveness in the operation of the apparatus due to not maintaining in the power unit, by means of the master cylinder and double check valve, a constant positive pressure, as has hithertofore been customary. My system is more sensitive as it is not necessary to-force the liquid through a double check valve. This arrangement nevertheless, in my present apparatus, permits during the pumping movement of the manual means back and forth, a withdrawal by suction, when necessary, of liquid from the master cylinder into the power unit, owing to the omission from the master cylinder of the double check valve and to the presence in the master cylinder of a rubber lip valve on the master cylinder piston through which liquid can pass to the power unit. In my apparatus, furthermore, I provide for balancing of the valves on the movable wall in a power unit and in a hand controlled vacuum regulating valve as well as in a vacuum controlled relay valve. so that the movement of the wall by diierential fluid pressures will not substantially alter the position of the valves into which they have been moved by the manual or other means. My invention also contemplates, not only the use of a movable wall in the power :yucatan unit in the form of a diaphragm, but instead the substitution of a piston for the same. Also, in constructing the power units which are arranged preferably in two stages, although only one stage may be used if' desired, the power plunger may be provided with a removable head for the piston of the plunger, so that, when desired, different piston sizes or pistons made of different materials may be substituted on the plunger. The piston forms a step on the plunger which produces with the cylinder, in which the power plunger is carried, the chamber which forces the liquid under power pressure to the brakes. This arrangement of the chamber is advantageous. owing to the pulling action exerted on the power plunger by the movable wall. In the power units, furthermore, the diaphragm is clamped in place in an advantageous manner by utilizing a clamping ring which exerts a compressing action on the outer edge of the rubber diaphragm in a radial direction, producing a uniformly tight seal of the rubber against the diaphragm casings without the necessity of utilizing a number of screws and so that the diaphragm may be held in place in this way by a clamping ring having a single tightening screw. Furthermore, my invention contemplates the utilization of a suitable vacuum regulating and adjusting valve for controlling the degree of vacuum applied in the operation of the power units. This vacuum regulating Valve may be located beyond the vacuum reservoir receiving the vacuum from the engine manifold and in advance of the power unit, but in the cas'e of trailer operation, said Valve is preferably located beyond the power unit on the tractor, and for trailer operation there is preferably also a separate vacuum reservoir provided with the same degree of vacuum as from the tractor reservoir and having for the trailer a relay valve which may be controlled, if desired, from a hand valve which regulates the degree of vacuum by the amount of air admitted. The brake operating means may be of the air-suspended type or, if desired, can be of the vacuum-suspended type. In tractor trailer installations, it is very important that the trailer brake be applied irrimediately before any appreciable braking is secured on the tractor. On slippery roads, and especially coming down grades, if the tractor should come in first on a fast application, the trailer would collide with the tractor and cause what is known as jackkniflngf In other words, the trailer, under severe conditions of this kind, could actually turn the vehicle over. Previously, devices have been known, called synchronizer valves, which boost the speed of operation in the trailer line. It is not necessary to use one of these valves in my two-stage larrangement for the reason that the trailer control line is attached to the first stage which operates before the second stage comes in, thereby assuring the operation of the trailer before the maximum braking is secured on the tractor. Furthermore, in the type of hand valve as well as the vacuum relay valve used in my apparatus, the valves themselves will open wide so as to permit substantially instantaneous application of the trailer brakes, and when the regulated pressures are attained, the particular valve shuts off when the diaphragm reaches its adjusted position.

While my invention is capable of embodiment in many different forms, for the purpose of illustration I have shown only certain forms thereof in the accompanying drawings, in which Fig. 1 is a diagrammatic plan view of an automobile chassis equipped with my apparatus;

Fig. 2 is a side elevation of the same;

Fig. 3 is a vertical section of the master cylinder used therein;

Fig. 4 is a vertical section of the air filter used herewith;

Fig. 5 is an end elevation of the tensifler unit and its mounting;

Fig. 6 is a longitudinal section of the check valve used in the apparatus;

Fig. 7 is a vertical section of the vacuum regulator valve;

Fig. 8 is a longitudinal section of the first stage intensifier unit showing the valve positions before the application of manual pressure but with the vacuum present;

Fig. 9 is a longitudinal section of the movable parts of the second stage intensifier unit showing the valves in lap position when some pressure is being received from the first stage power unit in Fig. 8;

Fig. 10 is a side elevation of the vacuum regulator valve;

Fig. 11 is an end elevation of the first stage intensifier unit;

Fig. 12 is an underneath view of the valve operating lever used in the first stage intensifier power unit;

Fig. 13 is a vertical section of the second stage intensifier unit;

Fig. 14 is a longitudinal section of the power plunger with a removable head in the first stage unitn first vstage inthe second stage unit;

Fig. 16 is a vertical section showing the valve leverage with the vacuum valve open;

Fig. 17 is a similar view of the vacuum and air valves closed;

Fig. 18 is a similar view with only the air valve open; a i

Fig. 19 is a diagrammatic view of the apparatus as applied to a trailer shown in the position before starting;

Fig. 20 is a vertical section of a vacuum suspended hand valve for independent trailer operation;

Fig. 21 is a Vertical section of the same valve taken at right angles to Fig. 20;

Fig. 22 is a vertical section of an air-suspended relay vacuum regulating valve;

Fig. 23 is a similar view of a part of a vacuumsuspended relay valve;

Fig. 24 is a vertical section of a modified form of power unit with a diaphragm for balancing the valves;

Fig. 25 is a similar section of another modified forni of power unit using a power piston instead of a diaphragm; and

Fig. 26 is a chart showing the advantages of using the balancing diaphragm for the valves in Figs. 24 and 25, the said advantages applying in like manner to the valve balancing diaphragm in the air and relay valves used in the trailer system.

Referring first to Figs. l to 18 of the drawings, I have shown an automobile chassis l having front and rear axles 2 and 3, carrying, respectively, four wheels 4 and 5, which are mounted in the usual way on vehicle frame members 6 and 1. Cooperating with each Vof the said wheels, there is the usual brake operating cylinder 8, having an air bleeder screw 8a, for operating a pair of brake shoes 9 and i0 adapted to coact Fig. 15 is a similar view of the power plunger in I with a brake drum |a. Each of said brake cylinders 8 has the usual exible connection connecting it to a transverse pipe I2 connecting the front or rear sets of brakes with a longitudinal pipe |3 connecting the brake cylinders of the four wheels together. The said pipe I8 has another branch pipe |4 which is provided to receive the hydraulic liquid under ation of the brakes.

Mounted on the said chassis there is a pedal I5 carried by a pedal le'ver I6 on a iixed pivot l1 located on the chassis. To the pedal lever |6 there is connected a link I8 by means of a pivot I9 and said link I8 has a pivotal connection 20 to a master cylinder lever 2|, carried by a fixed pivot 22, which is connected to a master cylinder 23 of any desired type, and which, for example, has the usual hydraulic cylinder 24 carrying an apertured piston 25, having a 1%" diameter and a 21/" stroke or any other desired dimensions, provided with the usual rubber seal 25a, which in addition forms a lip valve with holes 25h, connected by a Socket 26 to a link 21 and a pivotal connection 28 to the lower end of the lever 2|. In its retracted position the piston 25 uncovers a port 28 leading to a reservoir 29 containing the hydraulic liquid, which is received in the reservoir` 29 through the usual filling opening 29a having a vented cap 30. A port 30a connects the reservoir 29 to the body of the piston 25. The hydraulic liquid which is forced out of the master cylinder 23 by the piston 25 is delivered by a pipe 3| to an inlet connection 32 connected to a rst stage intensifier power unit 33. The liquid from the first stage intensifier power unit is delivered through an outlet connection 34 to a pipe 35 which has a connection 36 for feeding the pressure liquid to a second stage intensiiler power unit 31. -From the intensier power unit 31 an outlet connection 38 leads to a pipe 39 connected to the brake actuating cylinders through the pipe I4. It will be understood that in applying these intensifier power units in the installation on the automotive vehicle, either one or both of said power units 33 and 3l can be used alone although the unit 31 is better adapted for this purpose with any appropriate changes in the particular installation. rihe channel frame member 6 may be provided with two brackets 4| and 42 which are connected by bolts 43 to the channel frame member 6 and these brackets 4| and 42 may be connected by bolts 44 to supporting pads 45 and 46 provided on the intensifier power units 33 and 31, respectively, and having holes 41 and 48 in fiat surfaces 49 and 50 on plunger housings 5| and 52 for connecting them to the respective intensifier power units 33 and 31. As shown in Figs. 2 and 4, these plunger housings 5| and 52 have air inlets 53 and 54 which are connected by a T-shaped air inlet pipe 55 to an air cleaner 56 which is comprised of a headed tube 51 screwed into the pipe 55 and having a plurality of air ports 58 communicating with a chamber 59 lled with horsehair carried in a bell-shaped housing 60 which is provided in its lower portion with a retaining plate 6|, having air ports 62, the same being designed for retaining the body of horsehair in position. On account of positioning of the hydraulic passages and the air bleeding passages the individual power unit can be placed in the upright positions, as shown in Fig. 2, or in any other anticlockwise position therefrom through an arc of 90 to the position shown in Figs. 8 and 9.

pressure for the oper- A source of vacuum is provided for the intensi-r iler power units 38 and 81, comprising a pipe 8l connected to an' intake manifold 64 of the internal combustion engine 65 which drives the 5 automobile. Said pipe 63 leads to a nipple 88 screw-threaded into a check valve housing 81 having a check valve 68 therein with notches 88 around the edge thereof and which is adapted to seat against a valve seat ring 'l0 carried by said casing 61. This casing has screw-threaded therein a nipple 1| to which there is connected a pipe 12 having a connection 13 to a vacuum reservoir 14, which in turn has a connection to a pipe 18. The pipe 16 has a connection 11 which joins the same to an inlet opening 18 in casing 19 of an adjustable vacuum-regulating or reducing valve, see Figs. 'Zand 10. This valve casing 19 has an annular support 80 for a, diaphragm cover 8| having a vent opening 82. Around the edge of the cover 8| there are a plurality of screws 83 which pass through said cover and into the annular support 80 so asA to clamp in place a flexible diaphragm 84 of any suitable Arubberized fabric or material. At the center of the diaphragm 84 there is an opening 85 to support a transverse rod 86, one end 81 of which is located in the opening 82 and is provided with a screw-thread 88 carrying a nut 89 to hold in place clamping plates 90 and 9| on opposite sides of the diaphragm 84. The clamping plate 9|, furthermore, has bonded to the inner face of the same a synthetic rubber valve ring 92 which is adapted to seat on a valve seat 93 formed on a web 94 of the casing I9 which extends downwardly and to the right in Fig.'7 to form the valve seat 93. A retaining plate 85 for the valve ring 92 is supported against a shoulder 96 on the rod 86. The left hand end of said rod 86 has a shoulder 91 to support clamping plates 98 and 99 for a diaphragm |00 which iS clamped against said shoulder 91 by a nut |0 on the rod 86. The periphery of said diaphragm |00 has a gasket |02 on the same which holds the diaphragm |00 in place by an annular screw |03. Said screw |03 is internally screw-threaded to receive an adjusting screw |04 having a central hole |05 into which the left endvof the rod 86 passes` This hole |05, furthermore, leads to a.

spring chamber |06 in which there is a spring |01 for pressing the valve 92, 93 normally into an open position. Said spring seats at its left end against a shoulder |08 and at its other end against the nut |0l. A lock nut |09 holds the adjusting screw I 04 in its adjusted position. By this arrangement the spring |01 tends to hold the valve 92, 93 open. Also, the air pressing on the diaphragm I 00 balances the vacuum exerted on the valve ring 92. However, the arrangement is such that, as the diaphragm 84 is subject to the air pressure on one side and the vacuum on the other side, this no prevents exceeding the desired maximum vacuum, according to its adjusted position, so that the vacuum will not be too great and so as not to exceed the maximum brake line pressure. The vacuum transmitted through the valve casing 19 is communicated by an opening ||0 to a pipe and thence by branch pipes I I2 and I I3 to second stage and first stage intensier power units 81 and 33.

The construction of the first stage intensier l 'l0 power unit on servo pulsator generator power unit 33 is shown in Figs. 5, 8, and 1l. This power unit is comprised of a Iirst pulsator pressure generator including a housing 5| having a cylindrical bore 5|a and an inlet 32, leading to and from the master cylinder 23. This inlet is located in a screw modulating valve control plunger |24.

plug ||4 provided with a series of inlet openings ||6 between which there is a portion ||1 acting as a stop for the end of a valve plunger ||8 which has a tapered disk-like valve I |9 thereon cooperating with a valve seat ring provided with an annular seal |2| and held in place by a split ring |22 located in a recess in a longitudinal valve chamber |28 within the terminal portion gli) a is plunger is enlarged at the outer terminal to provide a first pulsator pressure generating piston having a peripheral seal |25 to seal the master cylinder applied liquid from the annular chamber |26 formed between plunger |24 and the surrounding cylinder 5| when valve ||9 is in closed position. The longitudinal valve chamber |23 communicates with a smaller valve chamber |21 leading to the annular chamber |26. In the valve chamber |21 there is provided a light spring |28 resting against a shoulder |29 in the chamber |23 for normally pressing the valve ||9 towards its closed position. A boss |30 retains the spring |26 in place. A series of radial passageways |3| lead from the left hand end of the valve chamber |23 to the annular chamber |26 for the passage of liquid when valve ||9 is open. Annular chamber |26 communicates through a passageway |32 with a second pressure generator including a second chamber |33 in which a second motor driven pis-` ton 201 having an effective surface area which 1 functions as a servo pulsator piston generator to supply volume at the pressure generated by the piston surface of said first generator piston |24 and thus reduce the required travel of the latter.

The plunger |24, at its left end, is guidably supported by a bushing |34, having inner and outer seals |35 and |36, said bushing having a series of diagonal air passageways |31 which connect an annular recess |33 in the face of the bushing with an air passageway |39 in the plunger housing 5 I. The recess |38 communicates with an annular packing chamber |40 which may contain any desired arrangement, such for example, as a retainer ring |40a, a leather seal |40b, a supporting ring |40c and a washer |40d. 'Ihe lip of the leather seal |40b is held in place by a garter spring |40e. Also, a split ring |4| is located in an annular recess in the chamber |40. Formed in the inner terminal of control plunger |24 is a cylindrical guide recess |42, in which there is loosely received in guiding relation one end of a flanged rod |43 acting as an aligning indexing pin, provided with a dowel and stop member |44 tightly pressed into a recess |45 in a diaphragm clamping plate |46. In this way, the plunger |24 is accurately positioned with regard to the diaphragm clamping plate |46 This 1s an aid in the assembly as the pin |43 restores the correct radial positions of the parts when being assembled. The plate |46 has clamped around the periphery of the same a diaphragm |41, of rubber or other flexible material, by means of a clamping ring |48 and screws |49. The outer periphery of the flexible diaphragm |41 is located between flanges |50 and |5| on anguiarly-dished diaphragm casing members |52 and |53 and outside the flanges |50 and |5| there is a split ringshaped'rectangular channel member |54, the free ends of which are fastened together by a bolt |55. By using the rectangular form this produces an inward radial pressure on the rubber which spreads the rubber transversely producing a tight seal without danger of pinching off the edges of the rubber. It will be noted that the inner face of the casing member |53 is fastened to the housing 5| by means of a clamping ring |56 and screws |51. It will, also, be noted that the other diaphragm casing member |52 has a screw-threaded coupling |58 for connection with the vacuum inlet pipe ||3.

The control plunger guide pin |43 has an annular stop flange |59 seating on the diaphragm clamping plate |46. Adjacent to the other terminal of stop flange |69, the end of control plunger |24 engages one end of a modulating valve operating lever |60. This lever |60 has two outwardly bowed portions |6| and |62 to provide a central opening |63, see Fig. 12. At the widest portion-o1' opening |63 the bowed portions |6| and |62 are provided with pivot pins |64 and |65 which pass through supporting ears |66 and |61 extending from the diaphragm clamping plate |46. Valve operating lever |60 carries screws |68 and |69 adapted to act as adjustable stops in the movement of the valve lever |60 against the face of the clamping plate or diaphragm hub or clamping plate |46. It will be noted in Fig. 12 that these screws |68 and |69 can be adjusted from the underneath side of said lever. Furthermore, at the other or work performing end of the lever |60 there is a bifurcated portion |10 to receive a pivot pin |1| for connection to a reciprocable valve plunger rod or stem |12 of the air and vacuum modulating valve assembly for controlling the admission and exhaust of atmospheric air to operate the diaphram |41.

The end of the lever |60 which is contacted by the control plunger |24 rests against two relatively light springs |13 carried in recesses |14 in the diaphragm clamping plate |46 functioning to normally restore the position of the vaive operating lever |60 when not being operated by control piunger |24. However,` when the control plunger |24 is being moved by the admission of pressure liquid through the inlet port 32 from master cylinder 23 this results in the movement of the modulating valve plunger |12 to the right in Fig. 8 which accordingly moves an annular synthetic rubber vaccum valve ring |15 to the right. Vacuum valve seat |18 for vacuum valve |15 is carried on a screw plug |19 mounted on a small flexible diaphragm of rubberized fabric or any other desired material. which is fastened to the left face of the diaphragm clamping plate |46 by means of a clamping and valve guiding ring |6| and screws |82. 'Ihis diaphragm |80 is clamped on the screw plug |19 between washers |83 and |83a carried on a tubular valve member |84 which passes through an opening |95 in the clamping plate |46. The tubular valve member |84 has bonded on its inner face a synthetic rubber valve ring |86 which cooperates with an annular valve seat |81 on the clamping plate |46. A valve spring |88 carried between the washer |83 and a shoulder |89 in the opening |85 normally keeps the valve ring |86 seated and the valve ring |15 is kept off its seat by the springs |13 so as to admit the vacuum to both sides of the diaphragm |41 through a passageway |90 in the screw plug |19 and openings |9| in the valve ring member |84. The opening communicates by means of an oval passageway |92, the narrow dimension of which is shown in the drawing, with an annular chamber |93 which in turn communicates with holes |94 in a tubular power plunger |95, which passes through the diaphragm supporting plate |46 and is secured thereto by a nut |96 located in place by a wire binding |91 passing through the nut |96 and through a screw |9|i. On the extreme end of the second generator plunger 

